Optical diffusion device

ABSTRACT

An optical diffusion device applied in a backlight module includes a plate, multiple light sources being disposed on one side of the plate; multiple optical microstructure provided with a longer axis and a shorter axis being disposed on the plate; a direction of the longer axis of each optical microstructure being approximately arranged in parallel with a direction extending from the light source, or a direction of the shorter axis being arranged approximately crossing a direction extending from the light source; better diffusion effect being provided to each light source through the shorter axis of the optical microstructure to increase optical quantum among light sources thus to eliminate the dim and dark regions among light sources for increasing general luminance of the backlight module.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention is related to an optical diffusion device, andmore particularly, to one applied in a backlight module to effectivelydistribute streams of light from light source for increasing luminanceof the entire backlight module.

(b) Description of the Prior Art

A backlight module is generally referred to a component that provide aback light source to a product and is currently applied in various typesof information, communication, and consumer products, e.g., liquidcrystal display (LCD), negative scanner, slider, or light panel forslides. Depending on the location of the light from its source to enter,the backlight module is available in edge lighting and bottom lighting.The edge lighting backlight module is usually applied in products, e.g.,portable computer that require power-saving, thinner and lighter inconstruction. To meet the requirements, a light source is usuallyprovided on an edge of the backlight module, and a light guide plate isdisposed to guide streams of light emitted from the light source to adisplay panel.

The bottom light backlight module is usually applied in a product thatrequires higher brightness, e.g. a TV set. As illustrated in FIG. 1, abottom light backlight module 1 is comprised of a frame 11, a reflectivecoating is applied or a reflection film 12 is attached on an inner sideof the frame 11; multiple light sources 13 are arranged and spaced atinterval in sequence; a diffuser 14 is disposed over those light sources13; one or a plurality of optical diffusion film 15 and one or aplurality of brightness enhancing film (BEF) 16 is disposed are disposedon the diffuser 14; and finally a display panel 17 is placed on top ofthe BEF to form a TFT-LCD.

Whereas the purpose of the optical diffusion device including thediffuser or diffusion film is only to permit uniform diffusion of thelight passing through; its effects to improve a phenomenon of dim anddark regions found with the liquid crystal module. Therefore, animprovement attempted to narrow down the dim and dark regions byextending a gap between those light sources 12 and the diffuser 13 foradmitting more streams of light emitted form those light sources 12 intothe diffuser 13; however, the structural design of the improvement forproviding limited effect and causing the backlight module to get thickerdefies the purpose of having a compact design for the liquid crystalmodule.

There are two types of process for manufacturing an optical diffusiondevice. One process involves formation of microstructures for diffusionon a surface of a substrate and another process is to coatmicro-particles on the surface of the substrate or mix them in thesubstrate. The process of coating those micro-particles usually fails tohigh uniformity and high yield; limited number of micro-particles to becoated fails to upgrade diffusion efficiency; and micro-particles couldeasily scratch other devices. The diffusion efficiency may be upgradedby mixing those micro-particles with the substrate, the lightpermeability remains low.

The microstructure formed on the surface of the substrate indicateseither irregularly fluctuating frosted glass structure or regular lensarray. The frosted glass type of structure was earlier used in the lightdiffusion structure, but its diffusion rate is low and its diffusiondirection is at random to fail providing diffusion in a given directionfor a device including fluorescent tube. Cylindrical lens arrayeffectively control diffusion direction and is currently designed in aform of continuous arc, sine wave, triangle, or square. The lens arrayis applied in a bottom lighting backlight module in an LCD as disclosedin US2003/0184993A1 and Japanese 2000-75102; wherein the former appliesthe lens array in a bottom lighting backlight module in an LCD toachieve diffusion effect and the latter applies a sine wave lens arrayin a collector. The design of continuous arcs with each greater than asemicircle achieve the best optical diffusion. As illustrated in FIGS.2(A) and 2(B), multiple cylindrical lenses 18 each in a sine wave formor any other form however fails to deliver effect of uniform diffusionof streams of light emitted from the light source (the arrow indicatesthe incident beams). Therefore, any of those optical diffusion devicesfails to solve the problem of dim and dark regions found with abacklight module of the prior art.

SUMMARY OF THE INVENTION

The primary purpose of the present invention is to provide an opticaldiffusion device that is applied in a backlight module to increase lightamong light sources thus to upgrade the general luminance of thebacklight module.

To achieve the purpose, the optical diffusion device of the presentinvention is essentially comprised of a plate, and multiple lightsources being disposed on one side of the plate to permit streams oflight emitted from those light sources are uniformly diffused throughthe optical diffusion device; wherein the plate includes multipleoptical microstructures respectively of longer axis and shorter axiswith the direction of the longer axis of each optical microstructureapproximately in parallel with a direction extending from the lightsource.

Whereas the curvature of the shorter axis is greater than that of thelonger axis, diffusion effect in the direction of the longer axis is waybelow than that in the direction of the shorter axis. By having thedirection of the longer axis of each optical microstructure arranged inapproximately parallel with the direction extending from the lightsource or having the direction of the shorter axis of each opticalmicrostructure arranged approximately crossing with the directionextending from the light source, a better diffusion effect is achievedfor the light passing through the shorter axis of each opticalmicrostructure thus to increase the light among multiple light sourcesfor eliminating the dim and dark regions among those light sources toincrease the general luminance of the backlight module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a construction of a bottom lightingbacklight module of the prior art.

FIGS. 2 (A) and 2 (B) are schematic views showing a construction of anoptical diffusion device of the prior art.

FIG. 3 is a perspective view of a construction of an optical diffusiondevice with light sources of the present invention.

FIG. 4 is a schematic view showing a construction of a first preferredembodiment of the present invention.

FIG. 5 is a schematic view showing a construction in A-A direction takenfrom FIG. 3.

FIG. 6 is a schematic view showing a construction of a second preferredembodiment of the present invention.

FIG. 7 is a schematic view showing a construction of a third preferredembodiment of the present invention.

FIG. 8 is a schematic view showing a construction of a fourth preferredembodiment of the present invention.

FIG. 9 is a schematic view showing a construction of a fifth preferredembodiment of the present invention.

FIG. 10 is a perspective view showing a construction of the presentinvention applied in a backlight module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 3, an optical diffusion device 2 of the presentinvention is essentially comprised of a plate 21 provided with anincident plane 211 and an irradiation plane 212 opposite to the incidentplane 211; multiple light sources 3 are disposed on one side of theplate below the incident plane 211 so that light emitted from thoselight sources 3 are uniformly distributed through the optical diffusiondevice 2.

The plate 21 contains multiple optical microstructures 22 respectivelyin longer axis and shorter axis with each microstructure 22 beingdisposed on the irradiation plane 212 in a first preferred embodiment asillustrated in FIG. 4 and a project of each optical microstructure 22 onthe irradiation plane 212 can be in an oval shape. Each opticalmicrostructure 22 as illustrated in FIG. 5 is related to an ovalhemispheric structure provided with a longer axis 221 and a shorter axis222 with the longer axis 221 provided in a direction that isapproximately in parallel with a direction 31 extending from the lightsource 3.

When applied in general as also illustrated in FIG. 5, the diffusioneffect is less satisfactory in the direction of the longer axis 221 thanthat in the direction of the shorter axis 222 since a curvature of theshorter axis 222 is greater than that of the longer axis 221. By takingadvantage that the direction of the longer axis 221 of each opticalmicrostructure being approximately in parallel with the direction 31extending from the light source 3, streams of light P1 (assuming thatthe quantum is 100%) upon entering into those optical microstructures22, a comparatively poor diffusion effect is achieved for those streamsof light passing through the longer axis 221 (if the optical quantum P2irradiated from the longer axis is 40%) while a better diffusion effectis achieve for those streams of light passing through the shorter axis222 (then the optical quantum irradiated P3 from the shorter axis is60%). That is, the optical quantum irradiated from a direction extendingfrom the light source 3 is lower and that going toward where among thoselight sources 3 is higher thus to increase the optical quantum amongthose light sources to eliminate the dim and dark regions otherwiseexisting among those light sources for increasing a general luminance ofthe backlight module.

In a second preferred embodiment as illustrated in FIG. 6, multipleoptical microstructures 22 are arranged at random on the irradiationplane 212 of the plate 21; each optical microstructure 22 is related toa structure in an oval hemispheric shape provided with the longer axis221 and the shorter axis 222; a direction of the longer axis 221 isapproximately in parallel with a direction 31 extending from the lightsource 3; multiple optical microstructure 22 are more intensivelyarranged over those light sources 31; and the optical microstructure 22may be made in a stick shape in a third preferred embodiment asillustrated in FIG. 7.

Multiple optical microstructures 22 are arranged at random on theirradiation plane 212 of the plate 21 in a fourth preferred embodimentas illustrated in FIG. 8, wherein the optical microstructure 22 isrelated to a structure in a rhombus cylindrical shape provided with along axis 221 and a shorter axis 222 and the direction of the short axis222 is approximately crossing with the direction 31 extending from thelight source 3.

In a fifth preferred embodiment as illustrated in FIG. 9, multipleoptical microstructures 22 are disposed on the irradiation plane 212 ofthe plate 21 with each optical microstructure 22 protruding from asurface of the irradiation plane 212; additional multiplemicrostructures 22 are disposed on the incident plane 211 with eachoptical microstructure 22 recessed in a surface of the incident plane211.

FIG. 10 shows a perspective view of a construction of having the opticaldiffusion device of the present invention applied in the backlightmodule. A first LCD panel 4 is disposed between multiple light sources 3and the optical diffusion device 2; a second LCD Panel 5 is disposed onthe optical diffusion device 2 so to provide a 3D display; and multipleoptical microstructures 22 are disposed on the irradiation plane 212 ofthe optical diffusion device 2 to correct a moiré effect found with theprior art that creates bright and dark ripples in vision.

When compared to the prior art, the present invention provides thefollowing advantages:

1. The microstructure is provided with longer and shorter axes toproduce different diffusion effects for effectively distribution streamslight emitted from light sources.

2. By having the direction of the longer axis of those opticalmicrostructures arranged in approximately parallel with the directionextending from the light source or having the direction of the shorteraxis of those optical microstructures arranged approximately in crossingthe direction extending form the light source for providing betterdiffusion effect to the light source through the shorter axis of thoseoptical microstructures, the optical quantum is increased among thoselight sources to eliminate the dim and dark regions otherwise existingamong those light sources for increasing the general luminance of thebacklight module.

3. With the optical diffusion device of the present invention applied ina 3D display and the optical diffusion device of the present inventiondisposed between the first and the second LCD panels, the moiré effectfound with a 3D display of the prior art to create ripples in vision iscorrected.

The prevent invention provides an improved structure of a opticaldiffusion device, and the application for a utility patent is duly filedaccordingly. However, it is to be noted that the preferred embodimentsdisclosed in the specification and the accompanying drawings are notlimiting the present invention; and that any construction, installation,or characteristics that is same or similar to that of the presentinvention should fall within the scope of the purposes and claims of thepresent invention.

1. An optical diffusion device comprising a plate provided thereonmultiple optical microstructures; and multiple light sources disposed onone side of the plate wherein each optical microstructure being disposedwith a longer axis and a shorter axis; a direction of the longer axis ofeach optical microstructure being approximately arranged in parallelwith a direction extending from the light sources.
 2. The opticaldiffusion device as claimed in Claimed in claim 1, wherein the plate isdisposed with an incident plane and an irradiation plane opposite to theincident plane; multiple light sources are disposed at where below theincident plane; each optical microstructure is disposed on theirradiation plane; and additional multiple optical microstructures aremore intensively arranged over those multiple light sources.
 3. Theoptical diffusion device as claimed in claim 2, wherein each opticalmicrostructure is further provided on the incident plane.
 4. The opticaldiffusion device as claimed in claim 2, wherein a projection from eachoptical microstructure on the irradiation plane is related to an ovalshape.
 5. The optical diffusion device as claimed in claim 1, whereineach optical microstructure is related to a structure in an ovalhemispherical, rhombus cylindrical or stick form.
 6. The opticaldiffusion device as claimed in claim 1, wherein the plate is disposedwith an incident plane and an irradiation plate opposite to the incidentplane, multiple light sources are disposed at where below the incidentplane; multiple optical microstructures are disposed on the irradiationplane; a first LCD panel is disposed between those light sources and theoptical diffusion device; and a second LCD panel is disposed on theoptical diffusion device to display 3D image.
 7. The optical diffusiondevice as claimed in claim 6, wherein multiple optical microstructuresare further disposed on the incident plane.
 8. An optical diffusiondevice comprising: a plate provided thereof multiple opticalmicrostructures; and multiple light sources disposed on one side of theplate; wherein each optical microstructure being disposed with a longeraxis and a shorter axis; a direction of the shorter axis of each opticalmicrostructure approximately crossing a direction extending from thelight sources.
 9. The optical diffusion device as claimed in claim 8,wherein the plate is disposed with an incident plane and an irradiationplane opposite to the incident plane; multiple light sources aredisposed at where below the incident plane; each optical microstructureis disposed on the irradiation plane; and additional multiple opticalmicrostructures are more intensively arranged over those multiple lightsources.
 10. The optical diffusion device as claimed in claim 9, whereineach optical microstructure is further provided on the incident plane.11. The optical diffusion device as claimed in claim 8, wherein eachoptical microstructure is related to a structure in an ovalhemispherical, rhombus cylindrical or stick form.
 12. The opticaldiffusion device as claimed in claim 8, wherein the plate is disposedwith an incident plane and an irradiation plate opposite to the incidentplane, multiple light sources are disposed at where below the incidentplane; multiple optical microstructures are disposed on the irradiationplane; a first LCD panel is disposed between those light sources and theoptical diffusion device; and a second LCD panel is disposed on theoptical diffusion device to display 3D image.
 13. The optical diffusiondevice as claimed in claim 12, wherein each optical microstructure isfurther provided on the incident plane.